`Rfast::sort_unique( integer(0L) )` results in crash

[solvi808]

Describe the bug
It's a very brief explanation, running Rfast::sort_unique( integer(0L) ) results in an instant crash on a fresh session.

To Reproduce
Rfast::sort_unique( integer(0L) )

Expected behavior
R session crash

Desktop (please complete the following information):

• OS: Debian GNU/Linux 12 bookworm (x86-64)
• R-Version 4.4.3
• Rfast-Version 2.1.5
• GCC-Version 12.2

[ManosPapadakis95]

This is because there is no any check about memory. For now, you can check it.